A method of manufacturing a semiconductor element includes forming a first silicon oxide film on a semiconductor wafer under a first film forming condition; forming a second silicon oxide film on the first silicon oxide film under a second film forming condition, a density of the second silicon oxide film being lower than a density of the first silicon oxide film; coating, with a photoresist, a region including the second silicon oxide film; exposing the photoresist using a photomask having an aperture and being disposed such that at least a portion of an edge of the aperture is disposed on the second silicon oxide film; removing a portion of the photoresist to form a photoresist pattern that has an overhang shape in a cross-section of the photoresist pattern; forming an electrode film on a region including the photoresist pattern; and performing lift-off by removing the photoresist pattern.